What it does in the body
- Serotonin (5-HT) neurotransmitter precursor
- Melatonin synthesis for sleep-wake cycle
- Niacin (vitamin B3) and NAD+ synthesis via kynurenine pathway
- Immune modulation (kynurenine pathway regulates T-cell tolerance)
- Protein synthesis
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | 4mg/kg/day (~280mg for 70kg) | WHO/FAO/UNU |
| Adult female | 4mg/kg/day (~240mg for 60kg) | WHO/FAO/UNU |
| Pregnancy | 5mg/kg/day | WHO |
| Children | 4-8.5mg/kg/day depending on age | WHO |
| Older adults | 4mg/kg/day; may benefit from higher intake for sleep and mood | WHO |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Turkey breast (cooked) | 0.34g per 100g | north-america |
| Chicken breast (cooked) | 0.32g per 100g | global |
| Pumpkin seeds | 0.58g per 100g | mesoamerica |
| Cheddar cheese | 0.32g per 100g | europe |
| Soybeans (cooked) | 0.24g per 100g | east-asia |
| Oats (raw) | 0.23g per 100g | global |
| Salmon (cooked) | 0.28g per 100g | global |
| Spirulina (dried) | 0.93g per 100g | global |
If you don't get enough
Mild: Insomnia, irritability, mild anxiety, carbohydrate cravings
Moderate: Depression, significant sleep disruption, impaired pain tolerance, cognitive dysfunction, pellagra-like symptoms if niacin also low
Severe: Severe depression, psychosis, pellagra (dermatitis, diarrhea, dementia), growth failure in children
Time to onset: Mood and sleep changes within 1-3 days of acute depletion (rapid tryptophan depletion test); chronic deficiency symptoms within 2-4 weeks
Too much
Upper limit: No established UL; supplemental doses >6g/day associated with eosinophilia-myalgia syndrome (historically linked to contaminated supplements in 1989)
Nausea, dizziness, drowsiness. Serotonin syndrome risk when combined with SSRIs/MAOIs. Eosinophilia-myalgia syndrome with contaminated supplements
How well you absorb it
85-95% intestinal absorption; brain uptake depends on competition with other large neutral amino acids
Helped by: Carbohydrate co-ingestion (insulin lowers competing BCAAs, increasing brain tryptophan ratio), Vitamin B6 (cofactor for 5-HTP to serotonin conversion), Iron
Hindered by: High BCAA intake (leucine, isoleucine, valine compete for blood-brain barrier transport), Chronic inflammation (IDO shunts tryptophan to kynurenine), Cortisol (upregulates TDO)
Cooking & storage
Relatively heat-stable during normal cooking. Corn-based diets (nixtamalization) can liberate bound niacin but don't significantly affect tryptophan content. Fermentation can increase free tryptophan availability.
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